Illustration: A mediaeval miniature transformed into a early modern engraving. The four great alchemists: Geber, Arnau, Rhazes and Hermes, in a mediaeval miniature of The Ordinall of Alchemy de Thomas Norton (MS British Library Add. 10302, c. 1477) and in an engraving printed in Theatrum Chemicum Britannicum by Elias Ashmole, London, 1652, p. 44.